January 3, 2014

Researchers have developed a new method of diagnosing wrist problems by creating “movies” of the radiocarpal joint in motion using a series of brief magnetic resonance imaging (MRI) scans, according to a study appearing in Tuesday’s edition of PLoS ONE.

The process is known as Active MRI, and according to the study authors, it could be used to diagnose subtle changes in physiology indicative of the onset of conditions such as wrist instability. The high-speed images produced using the technique are “like a live-action movie,” according to lead author and University of California-Davis radiology professor Robert Boutin.

“The movie can be slowed, stopped or even reversed as needed. Now patients can reproduce the motion that's bothering them while they're inside the scanner, and physicians can assess how the wrist is actually working,” Boutin said. “After all, some patients only have pain or other symptoms with movement.”

According to senior author Abhijit Chaudhari, an assistant professor of radiology at UC Davis, wrist instability typically occurs when the carpal bones become misaligned and impact joint function. Typically this occurs as the result of trauma that injures the ligaments between those wrist bones, and it can cause chronic pain, impair mobility and ultimately lead to osteoarthritis.

“Good outcomes in managing the condition are more likely with early diagnosis, when less-invasive treatments are possible,” the university said. “Methods such as dynamic computed tomography and fluoroscopy can image the moving wrist, but these approaches involve radiation and do not show soft tissue such as ligaments – a major part of the wrist's intricate architecture – as well as MRI scans.”

“MRI scans provide detailed anatomical information of wrist structures without using ionizing radiation, but they cannot help diagnose problems with bone or tendon position that are best seen when the wrist is moving,” Chaudhari added. “Active-MRI provides a detailed and 'real time' view of the kinesiology of the wrist in action using a widely available and safe technology.”

Ordinarily, a complete MRI exam takes between 30 to 45 minutes, with each image set requiring at least three minutes. That is nowhere near fast enough to create a video, the researchers said, so instead they developed a new MRI protocol that takes one image every 0.5 seconds and delivers a series of images in just 30 seconds.

In addition, Boutin, Chaudhari and their colleagues had to overcome the issue of imaging errors known as banding artifacts. Movement within the wrist bones can interfere with the scanner’s magnetic field, creating signal drop-offs and creating dark bands that can conceal the moving wrist. In order to address this problem, the investigators used dielectric pads to stabilize the magnetic field and give doctors a clear look at the wrist bones.

As part of their latest study, the investigators used the Active MRI process on 15 wrists belonging to 10 different participants, none of whom reported symptoms associated with wrist problems. The scans were taken during 10 minute exam sessions. During each, the subjects performing a variety of movements, including clenching their fists, rotating their wrists and waving their hands from side-to-side, the university explained.

“It's quite phenomenal that we can look inside the body while it's in action using MRI,” Boutin said. “Routine MRI provides exquisite details, but only if the body is completely motionless in one particular position. But bodies are made to move. We think Active MRI will be a valuable tool in augmenting traditional, static MRI tests.”

“Our next step is to validate the technology by using it on patients with symptoms of wrist instability,” added Chaudhari. “We also want to use Active-MRI to study sex distinctions in musculoskeletal conditions, including why women tend to be more susceptible to hand osteoarthritis and carpal tunnel syndrome.”